No drone, but I only go about 60mph when on the highway.
I have the Dynomax on a Camaro, which replaced the Flowmaster 40's, it was
a huge improvement.

Which Are louder
Dynomax or Borla and is it a significant dif?

For 10 years now I've been using Hooker Aero Chambers. Best muffler I have ever heard. Quite but measurable at idle and low rpm cruise, and they wake right up when you get on it but its a smooth deep sound like no other. And at highway speeds you can actually have a conversation w/o much of any drone. They flat out rock and I just ordered another set of them.

I had flow-masters on my black nova and there was a heavy drone at any highway speed. Hooker's are way better all the way around. I'm loading a video for you and will post it in a few minutes here.

https://i.ibb.co/nMSyPp6/IMG-0119.jpg

The Borla's are louder, the Dynomax also have a deeper tone.

Here's the Hooker Aero Chambers at idle. Hydraulic roller 355ci motor at 550" lift 236/240 duration. I'll load another cruise video here in a few minutes.

Down shifts start at 00:29 and up shifts start at 1:20. This will give you a great idea of the sound on the Hookers. That's my shameless muffler plug. lol

Alot louder?
The XR1dont come in Center/Offset which might present an issue for a 69 Camaro.

Your car sounds great!

Two things bother me with Aerochambers, 1) my system is 409 stainless which isnt the end of the world but I was hoping to keep it all 304 or 409

And 2). I read about alot of issues with Aerochambers rattling from something inside coming loose. Do you know of any issues or has Holley solved this defect? Seems like the threads in them were a few years old.

Never had anything rattle or loosen in any of mine and have never actually heard that. I have ordered 3 pairs of them in the past 6 years or so and also have a pair on my run stand exhaust to quieten things up when running in new motors. Those one are about 10-12 years old now and are still sound great with no rattles.

They do have these in stainless as well. Had the polished stainless 3" Aero Chambers on my 55

https://i.ibb.co/THnFc5p/55-Chev-Exhaust.jpg

Stainless doesn't appear to be available any longer